a kinder inquiry on how to create a treatment group for staggered DID estimation

[Saleh sharmah]

Dear members

I am trying to assess a country policy mandate on certain firm's outcomes in an international sample. I will be using staggered DID as countries have introduced the policed in different years while others did not.. My question here is that I would like to create a treatment gourp if the country mandates the policey =1 and zero otherize. I would like the dummy variable (1) to remain as one for the future years. my sample period is 2005-2020.

Thanks in advance for your kind help.

Here is an exmaple of my dataset:
nput str28 Country int(Policy1Year Year)
"ITALY" 2007 2005
"SWEDEN" 2005 2005
"BRAZIL" . 2005
"SWEDEN" 2005 2005
"FRANCE" 2005 2005
"UNITED STATES" . 2005
"JAPAN" 2005 2005
"JAPAN" 2005 2005
"SOUTH KOREA" 2012 2005
"GERMANY" 2005 2005
"UNITED STATES" . 2005
"FRANCE" 2005 2005
"UNITED STATES" . 2005
"INDIA" 2005 2005
"NETHERLANDS" 2006 2005
"FRANCE" 2005 2005
"UNITED STATES" . 2005
"JAPAN" 2005 2005
"UNITED KINGDOM" 2008 2005
"AUSTRALIA" 2005 2005
"CANADA" 2005 2005
"UNITED STATES" . 2005
"CANADA" 2005 2005
"AUSTRALIA" 2005 2005
"IRELAND" . 2005
"UNITED STATES" . 2005
"INDIA" 2005 2005
"INDIA" 2005 2005
"FRANCE" 2005 2005
"UNITED STATES" . 2005
"ITALY" 2007 2005
"SOUTH AFRICA" 2010 2005
"UNITED KINGDOM" 2008 2005
"FRANCE" 2005 2005
"AUSTRALIA" 2005 2005
"NETHERLANDS" 2006 2005
"PAPUA NEW GUINEA" . 2005
"SPAIN" 2005 2005
"JAPAN" 2005 2005
"FRANCE" 2005 2005
"AUSTRALIA" 2005 2005
"UNITED STATES" . 2005
"SWITZERLAND" . 2005
"SPAIN" 2005 2005
"CHINA" 2008 2005
"AUSTRALIA" 2005 2005
"PAKISTAN" . 2005
"JAPAN" 2005 2005
"JAPAN" 2005 2005
"UNITED STATES" . 2005
"SWEDEN" 2005 2005
"CHILE" 2015 2005
"JAPAN" 2005 2005
"SWITZERLAND" . 2005
"SPAIN" 2005 2005
"UNITED KINGDOM" 2008 2005
"UNITED STATES" . 2005
"SWEDEN" 2005 2005
"AUSTRALIA" 2005 2005
"JAPAN" 2005 2005
"SPAIN" 2005 2005
"UNITED KINGDOM" 2008 2005
"FRANCE" 2005 2005
"SWEDEN" 2005 2005
"UNITED STATES" . 2005
"UNITED STATES" . 2005
"UNITED STATES" . 2005
"GERMANY" 2005 2005
"UNITED STATES" . 2005
"SWITZERLAND" . 2005
"FINLAND" 2006 2005
"UNITED STATES" . 2005
"SPAIN" 2005 2005
"CHILE" 2015 2005
"UNITED STATES" . 2005
"AUSTRALIA" 2005 2005
"UNITED STATES" . 2005
"UNITED STATES" . 2005
"UNITED STATES" . 2005
"UNITED STATES" . 2005
"JAPAN" 2005 2005
"FRANCE" 2005 2005
"SWEDEN" 2005 2005
"CANADA" 2005 2005
"SWEDEN" 2005 2005
"JAPAN" 2005 2005
"UNITED STATES" . 2005
"JAPAN" 2005 2005
"GERMANY" 2005 2005
"UNITED KINGDOM" 2008 2005
"JAPAN" 2005 2005
"CANADA" 2005 2005
"UNITED STATES" . 2005
"UNITED STATES" . 2005
"UNITED KINGDOM" 2008 2005
"UNITED KINGDOM" 2008 2005
"NETHERLANDS" 2006 2005
"UNITED STATES" . 2005
"ITALY" 2007 2005
"GERMANY" 2005 2005
end

[Clyde Schechter]

by country, sort: gen treatment_group = !missing(Policy1Year)

Note, however, that for a staggered DID, the variable treatment_group is not used in the analysis.